By Eddie Wrenn
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Humans evolved from a prehistoric shark that roamed the seas more than 300 million years ago, say scientists.
The primitive fish named Acanthodes bronni was the common ancestor of all jawed vertebrates on Earth - including us, according to new research.
A re-analysis of a braincase dating back 290 million years shows it was an early member of the modern gnathostomes - meaning 'jaw-mouths' that include tens of thousands of living vertebrates ranging from fish to birds, reptiles, mammals and humans.
Acanthodes, a Greek word for 'spiny', existed before the split between the earliest sharks and the first bony fishes - the lineage that would eventually include human beings. Fossils have been found in Europe, North America and Australia.
Not so much Jaws as a member of the family: Meet one of your greatest ancesots, the acanthodes bronni
Compared with other spiny sharks it was relatively large, measuring a foot long. It had gills instead of teeth, large eyes and lived on plankton.
Professor Michael Coates, a biologist at the University of Chicago, said: 'Unexpectedly, Acanthodes turns out to be the best view we have of conditions in the last common ancestor of bony fishes and sharks.
'Our work is telling us the earliest bony fishes looked pretty much like sharks, and not vice versa. What we might think of as shark space is, in fact, general modern jawed vertebrate space.'
Cartilaginous fish, which today include sharks, rays, and ratfish, diverged from the bony fishes more than 420 million years ago. But little is known about what the last common ancestor of humans, manta rays and great white sharks looked like.
The acanthodians died out about 250 million years ago and generally left behind only tiny scales and elaborate suits of fin spines.
But armed with new data on what the earliest sharks and bony fishes looked like, the researchers re-examined fossils of Acanthodes bronni, the best-preserved species.
Prof Coates said: 'We want to explore braincases if possible, because they are exceptionally rich sources of anatomical information.
A re-analysis of the shark's brain-case, dating back 290 million years, shows it was an early member of the modern 'jaw-mouths'
'They are much better than scales, teeth or fin spines, which, on their own, tend to deliver a confusing signal of evolutionary relationships.'
The analysis of the sample combined with recent scans of skulls from early sharks and bony fishes led the researchers to a surprising reassessment of what Acanthodes bronni tells us about the history of jawed vertebrates.
Prof Coates said: 'For the first time, we could look inside the head of Acanthodes, and describe it within this whole new context. The more we looked at it, the more similarities we found with sharks.'
The study, published in Nature, found acanthodians as a whole, including the earliest members of humans' own deep evolutionary past, appear to cluster with ancient sharks.
This new revision of the lineage of early jawed vertebrates will allow paleontologists to dig into deeper mysteries, including how the body plan of these ancient species transformed over the transition from jawless to jawed fishes.
Added Prof Coates: 'It helps to answer the basic question of what is primitive about a shark. And, at last, we are getting a better handle on primitive conditions for jawed vertebrates as a whole.'
Environmental biologist Dr Maureen Kearney, of the National Science Foundation in the US which co-funded the research, said the study shows us 'important evolutionary transitions in the history of life, providing a new window into the sequence of evolutionary changes during early vertebrate evolution.'
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Grasping at straws,
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Not humans, just lawyers.
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Hark at all the know it alls.
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To billy, USA, 13/06/ - 22:43 -- [1] You ask "Would someone please resolve the obvious contradictions between entropy and evolution" -- This is a very old bit of creationist propaganda. There is NO conflict. The laws of thermodynamics refer to CLOSED systems. Whilst the universe as a whole can indeed be considered a closed system, locally there are many energy sources (stars) which are redistributing their energy. [2] Life itself is a series of essentially simple chemical reactions. It has been demonstrated only this year that both the precursor molecules for DNA and also cell membranes, can arise spontaneously. See "British scientists recreate the molecules that gave birth to life itself" (DM 27/01). and "Chemists Synthesize Artificial Cell Membrane" published in J. American Chem. Soc., Jan 2012. [3] The theory of evolution does not discuss the origin of life but, this subject (abiogenesis) is being actively investigated. [4] ID is religion dressed up as pseudo-science
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The first lawyer, perhaps?
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-----Would someone please resolve the obvious contradictions between entropy and evolution from no original order. (Species evolution...i.e. all birds evolving from a single bird is not being disputed here, but evolution from nothing is.) - billy, USA, 13/6/2012 22:43---- Billy, there is no contradiction at all - this notion is based on a serious misunderstanding of thermodynamics peddled by creationists. Entropy will increase in any closed system, however localised decreases in entropy can still occur provided the overall increase is preserved. The Earth is not a closed system though as it receives massive quantities of energy from the sun. In the Earth's open system, entropy can decrease allowing complex chemical processes to occur, which can in turn produce complex organised systems. Anyone dismissing evolution on the grounds of thermodynamics must also dismiss enzymes, photosythesis, growth and embryo development as fiction. Science gives answers, creationism sells lies.
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Oh what Hokem.
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Humans evolved from sharks? Makes sense. It certainly explains lawyers and car salesmen.
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Now we know where lawyers came from.
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Would someone please resolve the obvious contradictions between entropy and evolution from no original order. (Species evolution...i.e. all birds evolving from a single bird is not being disputed here, but evolution from nothing is.) So, you say we came from sharks. Where did the sharks come from? Where did all this originate? That is what evolution does not answer and intelligent design does. - billy, USA, 13/6/2012 22:43 ----- Hi Billy, you're talking about two separate, completely unrelated things. Evolution has absolutely nothing to do with the origin of life itself. That's like saying computer software needs to explain the origin of the plastic that computers are made of. The fact is that no-one (including both you and I) knows how life started. But hopefully one day we'll find out.
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